Various nanowire-based devices have emerged in recent years with many potentially useful applications. Nanowires are wire-like structures that typically have diameters of less that about 100 nanometers and can be used as an electrical interconnection between electronic devices. One method of forming nanowires is the vapor-liquid-solid (VLS) chemical synthesis process. Generally, this method involves depositing particles of a catalyst material such as gold or titanium on a surface of a structure on which it is desired to grow nanowires. The structure is placed in a chamber and heated to temperatures typically ranging between about 250° C. to about 1000° C. Precursor gasses including elements or compounds that will be used to form the nanowires are introduced into the chamber. The particles of the catalyst material cause the precursor gasses to at least partially decompose into their respective elements, some of which are transported on or through the particles of catalyst material and deposited on the underlying surface. As this process continues, nanowires grow with the catalyst particle remaining on the tip or end of the nanowires. Nanowires can also be formed by physical vapor deposition or by surface atom migration.
When the elements or compounds selected to form the nanowires are varied within the nanowire, these nanowires are referred to as “heterostructure nanowires.” In particular, a nanowire having a composition that varies along the longitudinal length of the nanowire is referred to as a “longitudinal heterostructure nanowire,” and a nanowire having a radially varying composition is referred to as “coaxial heterostructure nanowire.” Different regions or segments of single-composition or heterostructure nanowires can also be doped with electron donating and electron accepting impurities to form various semiconductor devices within the nanowires, such as p-n, p-i-n, p-n-p, and n-p-n junctions that enable the nanowires to be used as diodes, field-effect transistors, or photonic devices.
However, implementing nanowires in devices that can be employed in a wide range of useful light-emitting and light-detecting devices remains a challenge.